A conventional photovoltaic system has been provided with photovoltaic cells, a dispersed power supply and a ground fault detector circuit (for example, see Patent Literature 1). The dispersed power supply is configured to convert DC voltage of the photovoltaic cells into AC voltage. The ground fault detector circuit is configured to detect a ground fault in direct current paths connecting the photovoltaic cells and the dispersed power supply.
The ground fault detector circuit includes a zero-phase-sequence current transformer having a detection core through which the direct current paths are threaded, and is configured to detect a ground fault current flowing from an output of a secondary winding wrapped around the detection core through the secondary winding.
With the ground fault detector circuit, there is a possibility that the detection core will be magnetized by a DC current flowing through the direct current paths because the detection core is arranged to be electromagnetically coupled to the direct current paths. The detection core being magnetized may make current detection precision worse.